Spinneret distribution plate



2 Sheets-Sheet 1 I HZ U J. S. COBB, JR

SPINNERET DISTRIBUTION PLATE NWN Dec. 28, 1965 Filed July 24, 1965 55: as jo a Dec. 28, 1965 J. 5. COBB, JR 3,225,383

I SPINNERET DISTRIBUTION PLATE Filed July 24, 1963 2 Sheets-Sheet 2 United States Patent 3,225,333 NERET DHSTRTBUTTON PLATE James Stanley Cobb, Era, Martinsvilie, Va., assignor to E. 1. du Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware Filed July 24, 1963, Ser. No. 297,328 4 tllairns. (Cl. l88) This invention relates generally to the production of filaments from molten organic compositions and, more particularly, to a spinneret assembly useful in the spinning process.

The melt-spinning of synthetic linear polymers through an apparatus installation including a metering pump, a filter block, and a spinneret plate is disclosed in US. Patent No. 2,266,368 to Hull et a1. and in U.S. Patent No. 2,278,875 to Graves. Such installations are particularly useful in the melt-spinning of polyamides and polyesters, e.g., polyhexamethylene adipamide and polyethylene terephthalate. It has frequently been observed, however, that the filaments are not entirely uniform in quality, particularly denier, despite efforts to supply the polymer to the spinneret pack at a constant pressure, temperature and rate. One reason for this lack of uniformity between fila rents is that the molten polymer near the periphery ot the spinneret plate is cooler than the polymer near the center of the plate owing to heat losses from the side of the chamber as the polymer passes slowly through the filter block. Another reason, now believed to be the major cause, is that the heat loss through metal parts, particularly the spinneret and its holding ring, causes a temperature gradient across the spinneret plate. The difference in temperature between the center and periphery of the spinneret may amount to 5 C. or even more. Accordin ly, the polymer extruded-near the circumference of the spinneret plate is extruded more slowly and solidifies rnore rapidly in the filament than does the polymer extruded near the center of the plate, resulting in nonuniformities in the yarn properties and denier. Denier variations not only show up in the final fa ric but also are troublesome during its fabrication in that heavy denier filaments in a group of filaments, i.e., in a thread, do not follow the same path as the lighter filaments when going around guides or pins, but loop out. These loops often catch and break, necessitating a shutdown of the fabrication process.

It is the general objective of the present invention to provide an improved spinneret assembly in order to obtain better denier uniformity between individual filaments and good total-denier uniformity between two or more threads receiving polymer from the same metered stream. A more particular objective is the provision of an improved spinneret distribution system which compensates for a temperature gradient across the spinneret plate.

These and other objects are accomplished with an imperforate distribution plate sandwiched between the filter block and spinneret plate of a spinneret pack and provided with distribution channels in its upper face leading to or near the periphery of the plate, tapered cavities in the bottom face and opposed slots at or near the periphery, each slot connecting some or all of the distribution channels with a cavity. Each cavity extends from its slot toward the opposed slot and has its maximum depth adja cent the slot with which it communicates.

The invention will be more readily understood by reference to the following detailed description wherein reference is made to the accompanying illustrations. Referring now to the drawings:

FIGURE 1 is a cross sectional view of a spinneret assembly including the distribution plate of the present invention;

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FIG. 1a is a fragmentary enlargement of the distribution plate and filter block of FIG. 1;

FIG. 2 is a view along line 11-11 of FIG. 1, i.e., a bottom view of the pack assembly with the spinneret plate and holding ring removed;

FIG. 3 is a similar view of a second embodiment;

FIG. 4 is a cross sectional view of a spinneret assembly including a different filter block and a third embodiment of the distribution plate; and

FIG. 5 is a view along line V-V of FIG. 4.

The embodiment illustrated in FIGS. 1, 2 includes, as components, a spinneret plate 10 and a distribution plate 12 attached to a filter block 14 by bolts 16. This assembly is held in position against a spinning machine 18 by a conventional holding ring 20.

Filter block 14 has two identical filtration cavities 22, each containing the usual screens, sand, etc. (not shown), which function to filter separate metered streams of molten polymer received from conduits 23, 24 in machine 18. Filtered polymer is discharged from cavities 22 through holes 25, 26, respectively.

spinneret plate 10 is provided with four different groups of aligned holes 28, each of which spins a thread of three filaments. Where additional holes are provided, they may be arranged in two or more staggered rows in order to insure elfective quenching.

In its upper face, distribution plate 12 has two branched channel systems 29, 30 through which the separate metered streams flow from holes 25, 25 outwardly to opposed slots 31, 32 and thence to tapered cavities 2 35. As illustrated, slots 31, 32 are opposed and located adjacent the periphery of plate 12. Each tapered cavity has its maximum depth at and is approximately coextensive in width with its associated slot. For example, cavity 35 has its maximum depth beneath slot 32 and tapers downwardly to a minimum depth adjacent the center of plate 12.

The operation and utility of the embodiment shown in FIGS. 1, 2 will be aparent from the following example.

Example I Nylon is melted, brought to a temperature of 280- 295 C. and then pumped in separate metered streams through conduits 23, 24- to the filtration cavities 22. The channels, slots and tapered cavities in distribution plate 12 define separate flow paths between filter block holes 25, 2e and the associated spinneret holes 28. Spinneret plate Eli? is designed to spin four threads of 20 denier (2.2 Tex), seven filaments per thread. Thus, each metered stream is divided into two threads, each having seven filaments, each filament being slightly less than three denier per filament. The channels 29, 36 are 0.156 inch wide and 0.031 inch deep. The tapered cavities 34, 35 are 0.75 inch Wide by 1.375 inch long, with a minimum depth of 0.027 inch and an angle of taper of 452.

Measurements of the flow of the individual filaments issuing from each spinneret capillary or hole 28 shows that the denier variations between individual filaments and between the threads were reduced to less than 2%. This compares with the 15% variation which occurs when the distribution plate 12 is replaced with a thin gasket to form a single distribution space below each sand cavity 22. Since the temperature gradient between the center and periphery of the spinneret plate 10 is substantially the same in both instances, the lower denier variations achieved with the distribution plate 12 are attributable to the different pressure drops across the various spinneret holes 28 which differences are caused by the taper in cavities 34, 35. In other words, the slightly higher pressure drop across an outer hole 23 compensates for the slightly lower plate temperature at that location.

In the past, it has been considered essential that each group of filaments be fed by a separate metered stream from a metering pump. Using the improved apparatus of this invention, it has been found possible to divide and equally distribute a metered stream into two or more threads and still achieve better denier uniformity between the two threads.

When additional filaments per thread are desired, it is not only necessary to arrange the spinneret holes in staggered rows but also to increase the width of each tapered cavity 34. This can be done to some extent without any ill effects; however, if the cavity width of the embodiment illustrated in FIG. 2 is extended too much, there is a tendency to form two separate streams, i.e., the warm material coming from center branches of the channel system tends to stay in the center of the communicating tapered cavity whereas colder material coming from outer branches tends to flow to the outer edge of the cavity, giving a variation in denier between the front filaments and the back filaments in a thread. This difficulty can be overcome by modifying the channel system in the upper face of the distribution plate, as shown in PEG. 3.

Referring to FIG. 3, it is seen that the channel systems 29', 30 are branched to a significantly lesser extent than those of FIG. 2 in order to compensate for the greater relative width of tapered cavities 34', 35, leaving a wider groove above and beyond the lengths of slots 31, 32'. It is important that the velocity of polymer flowing through each slot be the same at all points, i.e., the velocity at the center should be the same as the velocity at the two ends. In the embodiment shown, with eight distribution holes 26', the projections 33 direct the polymer flow so that there is a uniform velocity through the length of slot 32'. This modification is required when cavity width equals or exceeds cavity length.

An adaptation of the distribution principles of the present invention to a spinneret assembly in which the filter block has but a single cavity has been illustrated in FIGS. 4 and 5. As shown, a filter block 42 has nine distribution holes 44 which direct polymer from a filter cavity 46 to a circular collection space 48. Any variations in polymer fiow through the filtering means are overcome by feeding all the polymer to the collection space 48. Directly below the sandholder 42 is a distribution plate 50 and a spinneret plate 52. The elements 42, 50, '52 and appropriate gaskets are held together by a ring 53 which has an upper extension (not shown) threaded into the spinning machine.

Channel 54 is in the otherwise fiat face of distribution plate 50 which is adjacent filter block 42 and the tapered cavities 56 are in the opposite face, i.e., adjacent the spinneret plate 52. Each branch of channel 54 has the same width as each tapered cavity 56. Slots 58, near the outer periphery, connect the opposed branches of channel 54 with the tapered cavities 56. As in previous embodiments, the maximum height of each tapered cavity 56 is at its outermost extremity. The spinneret plate 52 has fourteen holes 60, of equal size and arranged in a single row. The fourteen monofilaments are quenched, collected and wound-up on individual packages in accordance with known procedures. Excellent denier uniformity is obtained.

In operation, polymer is metered to the filter cavity 46, directed into the collection space 48 by the distribution holes 44, split into two flows, one through the righthand branch of channel 54 and the other through its lefthand branch, through opposed slots 58, and finally distributed to the holes 60 through the tapered cavities 56.

In practice, it has been found that a differential of 24 psi. between the pressure drops in the outer and centermost spinneret holes is required to compensate for a temperature differential of 35 C. Such a pressure gradient is insured by a proper design of the channels and tapered cavities in the distribution plate. Their dimensions can be calculated from known factors such as polymer viscosity and cavity width. Since the pressure gradient increases with an increase in throughput, it would appear that a given design would be useful at only one flow rate. However, with an increase in flow rate, the temperature differential also increases and is compensated for by the greater pressure gradient. The existence of this relationship is substantiated in the following example.

Example 11 The apparatus and process of Example I were used to spin four threads of 4013 yarn from two metered streams. The spinning throughput was varied i1()% and there was no significant difference in denier between the threads.

Total denier variation Wind-up speed (y.p.rn.): between threads, percent It will be aparent that the distribution system disclosed herein may be changed and modified in many ways without departing from the spirit of the present invention which is, therefore, intended to be limited only by the scope of the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A spinneret assembly comprising sandwiched filter block, distribution plate and spinneret plate elements, said filter block and spinneret plate elements having spaced flow holes, said distribution plate being provided with a pair of opposed slots adjacent its periphery, channels in the upper face and a pair of tapered cavities in the lower face thereof, each cavity tapering downwardly from a maximum depth at its slot, said channels, slots and cavities defining separate flow paths between the filter block and spinneret plate holes.

2. The assembly of claim 1 wherein each cavity extends from a slot toward the opposed slot and has its maximum depth and width at its slot.

3. A spinneret assembly comprising filter block and spinneret plate elements provided with spaced flow holes and a distribution plate sandwiched between said elements, said distribution plate being imperforate except for a pair of spaced opposed slots, there being channels and a pair of cavities in the respective upper and lower faces of said distribution plate, each cavity extending from one of said slots toward the opposed slot and being tapered from a maximum depth at said one slot, said channels, slots and cavities defining separate flow paths between the filter block and spinneret plate holes.

4. The assembly of claim 3 wherein said channels have branches, each branch being in communication with at least one hole in the filter block.

References Cited by the Examiner UNITED STATES PATENTS 2,385,856 10/1945 Hayes 18-8 2,398,729 4/1946 Taylor et a1. 188 2,971,219 2/1961 Hill 18-8 J. SPENCER OVERHOLSER, Primary Examiner.

MICHAEL V. BRINDISI, Examiner. 

1. A SPINNERET ASSEMBLY COMPRISING SANDWICHED FILTER BLOCK, DISTRIBUTION PLATE AND SPINNERET PLATE ELEMENTS, SAID FILTER BLOCK AND SPINNERET PLATE ELEMENTS HAVING SPACED FLOW HOLES, SAID DISTRIBUTION PLATE BEING PROVIDED WITH A PAIR OF OPPOSED SLOTS ADJACENT ITS PERIPHERY, CHANNELS IN THE UPPER FACE AND A PAIR OF TAPERED CAVITIES IN THE LOWER FACE THEREOF, EACH CAVITY TAPERING DOWNWARDLY FROM A MAXIMUM DEPTH AT ITS SLOT, SAID CHANNELS, SLOTS AND CAVI- 